The BBC micro:bit has a built in Bluetooth 4.0 - Bluetooth low energy (BLE)
BLE is targeted for very low power devices, devices that can run on a coin cell battery for months or years.
Bluetooth Pairing
To pair the Bluetooth with a Phone, Pad or computer select the devices Bluetooth settings
To start the BBC micro:bit Pairing mode while holding down both A and B buttons press the Reset button, keep holding down the A and B buttons until it starts scrolling "PAIRING" on its LED display.
Then on your device select scan
It should find BBC micro:bit
Press button A on the micro:bit and it will display a six digit number to type into your device to complete the pairing.
Once accepted the micro:bit will respond with a ✔ tick on its LED display
If it displays an X then you need to try again.
Once paired press the micro:bit Reset (pairing is saved)
You will need to pair each time you Upload a new Hex file via the USB interface.
There are a few Apps available to down load, you may need to connect to the "BBC micro:bit" in the Bluetooth settings on your device.
A good test Android app is available called micro:bit Blue
Programming Bluetooth
Limitations
NOTE you cannot use BBC micro:bit Bluetooth with MicroPython due to memory limitations.
Android 4.4 and above
Coding
Use C++
Lancaster University have working examples of the coding required using Yotta
Bluetooth Button A and Button B
Uses Bluetooth notifications and the ButtonActivity
call bluetooth_le_adapter.setNotificationState
The "Button Service" responds with 3 values, 0=Not pressed, 1=Pressed and 2=Long press.
Useful links
ui.ButtonActivity.java Android
see also